[L12]_HVAC Hydronic Cooling System Flashcards
IND405
Increasing the ∆t of chilled water from 8°F to 12°F results in which of the following benefits?
A. Reduced circulating pump horsepower by 50%
B. Increased chiller efficiency and reduced GPM by 33%
C. Higher system pressure losses
D. No significant changes
[L12]
B. Increased chiller efficiency and reduced GPM by 33%
[L12]
IND405
True/False: Chilled-water systems must avoid temperatures below 32°F to prevent reservoir water freezing.
[L12]
True
[L12]
IND405
Match the chiller type with its characteristic:
1. Air-Cooled Chillers
2. Water-Cooled Electric Chillers
3. Water-Cooled Absorption Chillers
A. Requires high-pressure steam or natural gas as energy source
B. Typically located outdoors with harsh environmental exposure
C. Offers long life expectancy and is ideal for substantial cooling loads
[L12]
1 = B. Typically located outdoors with harsh environmental exposure
2 = C. Offers long life expectancy and is ideal for substantial cooling loads
3 = A. Requires high-pressure steam or natural gas as energy source
[L12]
IND405
Which type of chiller has the highest part-load efficiency?
A. Water-Cooled Steam Turbine Chiller
B. Water-Cooled Electric Chiller with Magnetic Bearings
C. Air-Cooled Chiller
D. Single-Stage Absorption Chiller
[L12]
B. Water-Cooled Electric Chiller with Magnetic Bearings
[L12]
IND405
True/False: Water-cooled chillers are generally more energy efficient than air-cooled chillers.
[L12]
True
[L12]
IND405
Which dual-temperature system offers the most flexibility for simultaneous heating and cooling?
A. Two-Pipe System
B. Four-Pipe Independent System
C. Four-Pipe Common System
D. Single-Pipe System
[L12]
B. Four-Pipe Independent System
[L12]
IND405
A control valve is needed for a 30-Ton cooling coil with a 12°F ∆t and a pressure drop of 5 psi. What is the required Cv of the valve?
[L12]
Cv = 26.83
[L12]
IND405
Antifreeze solutions in chilled-water systems does not help prevent freezing but can cause corrosion if inhibitors are not used.
[L12]
False
[L12]
IND405
What is the typical chilled-water flow rate per ton of cooling?
A. 0.5 GPM
B. 1-1.5 GPM
C. 2-2.5 GPM
D. 3-4 GPM
[L12]
B. 1-1.5 GPM
[L12]
IND405
True/False: Pressure loss correction is unnecessary for glycol solutions above 160°F.
[L12]
True
[L12]
IND405
Match the air elimination type with its function:
1. Air Separator
2. Manual Vent
3. Automatic Air Removal Device
A. Removes trapped air at high points in the system
B. Installed at points of lowest solubility to remove air continuously
C. Provides servicing capability without system drainage
[L12]
1 = B. Installed at points of lowest solubility to remove air continuously
2 = A. Removes trapped air at high points in the system
3 = C. Provides servicing capability without system drainage
[L12]
IND405
Ethylene glycol solutions can increase system viscosity, potentially reducing pump efficiency.
[L12]
True
[L12]
IND405
What is recommended to preserve the life of a system using antifreeze solutions?
A. Flush the system with hard water before injecting glycol.
B. Use waters low in chloride and sulfate ions to prepare the solution.
C. Limit operating temperatures to below 120°F.
D. Avoid cleaning and flushing the system.
[L12]
B. Use waters low in chloride and sulfate ions to prepare the solution.
[L12]
IND405
True/False: A diaphragm tank is required in chilled-water systems to control air and pressure fluctuations.
[L12]
True
[L12]
IND405
A chilled-water system has a total head loss of 95-ft, a flow rate of 400-GPM, and a pump efficiency of 75%. What is the required pump horsepower?
[L12]
HP = 12.79 ≈ 15 HP
[L12]
